Vehicle control device

ABSTRACT

A vehicle control device controls operation of a vehicle provided with a transmission having a direct gear and normal gears including an overdrive gear having a lower gear ratio than the direct gear. The device includes a travel segment determination unit which determines a forward travel segment having a different road slope from a current travel segment, a current gear position selection unit that selects a current gear position in accordance with a shift pattern, a forward gear position selection unit that selects a forward gear position based on a travel resistance of the vehicle in the forward travel segment, and a shift control unit that maintains a gear position as the direct gear while the vehicle travels in the forward travel segment, when a gear position of the transmission in the current travel segment is the overdrive gear and the forward gear position is the direct gear.

TECHNICAL FIELD

The present disclosure relates to a vehicle control device, and moreparticularly to a technique of selecting a gear position of atransmission mounted on a vehicle.

BACKGROUND ART

A technique of setting a shift schedule, in which fuel consumptionamount on a travel route is minimized, by estimating drive force of avehicle on a travel route in accordance with road information on atravel route from a current position of the vehicle to a target positionand by comparing the estimated drive force with a fuel consumption mapstored in advance, has been proposed (see Patent Literature 1).

CITATION LIST Patent Document

-   Patent Literature 1: JP-A-H09-21457

SUMMARY OF THE INVENTION Technical Problem

Large vehicles such as trucks and buses may be provided with atransmission called Automated Manual Transmission (hereinafter, referredto as “AMT”). AMT is a transmission which automatically shifts a gearposition of a transmission by moving a single rib in a manualtransmission according to the related art by means of an actuator.

The final drive force of the vehicle depends on a gear position selectedby the AMT. Here, the AMT is provided with a large number of gears, andresistance of squeezing at each gear position may be different from eachother. The difference in resistance of the squeezing at each gearposition affects the fuel consumption amount of engines mounted onvehicles. Therefore, it is considered that there is room for improvementin a technique of selecting a gear position based on the fuelconsumption amount of the vehicle.

An object of the present disclosure is to provide a vehicle controldevice which can improve the technique of selecting a gear position in avehicle provided with an automated manual transmission.

Solution to Problem

The vehicle control device according to the present disclosure is avehicle control device that controls operation of a vehicle providedwith a transmission. The transmission includes: a direct gear thattransmits engine power, which is input via an input shaft, to an outputshaft not via a counter shaft, and that directly couples the input shaftto the output shaft; and a normal gear that transmits the engine powerto the output shaft via the counter shaft, and that includes anoverdrive gear having a gear ratio lower than a gear ratio of the directgear. The vehicle control device includes: a travel segmentdetermination unit that determines a forward travel segment ahead of thevehicle in a travelling direction, the forward travel segment having aroad slope different from a road slope of a current travel segment wherethe vehicle currently travels; a current gear stage selection unit thatselects a current gear position, which is a gear position of thetransmission in the current travel segment, in accordance with apre-defined shift pattern; a forward gear position selection unit thatselects a forward gear position, which is a gear position of thetransmission in the forward travel segment, based on a travel resistanceof the vehicle in the forward travel segment estimated based on a roadslope of the forward travel segment and a speed of the vehicle; and ashift control unit that maintains a gear position of the transmission asthe direct gear while the vehicle travels in the forward travel segment,when a gear position of the transmission in the current travel segmentis the overdrive gear and the forward gear position is the direct gear.

The shift control unit may downshift a gear position of the transmissionto the direct gear when the vehicle reaches the forward travel segment,and may maintain the gear position of the transmission as the directgear even in a case where the current gear position selection unitselects the overdrive gear while the vehicle travels in the forwardtravel segment.

The shift control unit may downshift a gear position of the transmissionto the direct gear when the vehicle reaches the forward travel segment,on condition that a road slope in the forward travel segment is anupslope equal to or greater than a predetermined value.

Advantageous Effects of the Invention

According to the vehicle control device of the present disclosure, it ispossible to improve a technique of selecting a gear position in avehicle provided with an automated manual transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an outline of a vehicle according to anembodiment.

FIG. 2 is a diagram schematically showing an internal configuration ofthe vehicle according to the embodiment.

FIG. 3 is a diagram schematically showing a functional configuration ofa vehicle control device according to the embodiment.

FIG. 4 is a graph schematically showing an example of a fuel consumptioncontour map of an engine according to the embodiment.

FIG. 5A is a graph schematically showing an example of a fuelconsumption contour map of a direct gear.

FIG. 5B is a graph schematically showing an example of a fuelconsumption contour map of a normal gear.

DESCRIPTION OF EMBODIMENTS Summary of the Embodiment

FIG. 1 is a diagram showing an outline of a vehicle V according to anembodiment. An outline of the vehicle V according to the embodiment willbe described with reference to FIG. 1. The vehicle V according to theembodiment is a large vehicle provided with an AMT, which is driven byan engine such as a diesel engine.

In recent years, a computing device such as an electronic control unit(ECU) mounted on a vehicle has been widely used to automatically selecta gear position of a transmission so that a vehicle overcomes travelresistance to travel and fuel consumption of the vehicle is improved.Details will be described below, and the selection of the gear positionin the vehicle is performed by selecting, with reference to a fuelconsumption contour map of the engine, a gear position improving thefuel consumption of the vehicle from gear positions capable ofgenerating torque which overcomes the travel resistance of the vehicle.

During travelling of the vehicle, an acceleration of the vehicle isproportional to an amount obtained by subtracting travel resistance ofthe vehicle from drive force of the vehicle, and is inverselyproportional to weight of the vehicle. Accordingly, the ECU mounted onthe vehicle estimates the travel resistance of the vehicle from thedrive force of the vehicle, the weight of the vehicle, and theacceleration of the vehicle, and selects a gear position capable ofgenerating a torque which overcomes the travel resistance. However, whenthe ECU estimates the travel resistance using the acceleration of thevehicle, the ECU can estimate the travel resistance of the vehicle at acurrently traveling position, but cannot estimate the travel resistanceat a position ahead of the currently traveling position.

When the ECU determines the travel resistance by estimation, calculationaccuracy of the travel resistance is not necessarily high. Therefore, agear position is selected based on the travel resistance whose accuracyis not necessarily ensured, and thus it is not necessarily ensured thatthe selected gear position is a gear position which improves the fuelconsumption of the vehicle. Therefore, the ECU of the vehicle Vaccording to the embodiment estimates the travel resistance at a forwardposition by acquiring slope information of a road at the position aheadof the currently traveling position. A summary of a method forestimating the travel resistance at the forward position by acquiringslope information by means of the vehicle V according to the embodimentwill be described below.

The vehicle V according to the embodiment has a satellite navigationfunction of acquiring position information showing a current position ofthe vehicle V based on information received from a navigation satellite.In addition, the vehicle V stores slope information of a road on whichthe vehicle V travels. The vehicle V may have an autonomous navigationfunction of acquiring a current position of the vehicle V based on anoutput value of an acceleration sensor or the like without using theinformation received from the navigation satellite.

The ECU of the vehicle V prefetches, based on the slope information ofthe road and the position information of the vehicle V, slopeinformation of a road on which the vehicle V will travel in the nearfuture. In FIG. 1, the vehicle V is traveling in a “current travelsegment” having a point A as a start point and a point B as an endpoint. In the example shown in FIG. 1, a road on which the vehicle V istraveling is an upslope above a certain level in a “forward travelsegment” having the point B as a start point and a point C as an endpoint. The “forward travel segment” is a travel segment whose averageslope of the road is different from that of the current travel segmenton which the vehicle V is currently traveling, and is a travel segmentahead of the vehicle V in a travelling direction.

The slope information of the forward travel segment prefetched by theECU is determined from the slope information stored by the vehicle V andthe position information of the vehicle V. The travel resistance of thevehicle V is dominated by slope resistance, air resistance, and rollingresistance, and the slope resistance among the above resistance can beestimated. As a result, the ECU can estimate the travel resistance ofthe forward travel segment.

The fuel consumption of the vehicle V is not only affected by specificfuel consumption (that is, the amount of fuels consumed by an engine togenerate predetermined drive force) of an engine provided in the vehicleV, but also affected by sliding resistance inside the engine or a lossin a power transmission path of the engine. Here, the loss in the powertransmission path of the engine is, for example, a loss caused bytransmission efficiency of each gear provided in the transmission.

Therefore, the vehicle V according to the embodiment refers to a fuelconsumption contour map in consideration of the transmission efficiencyof each gear provided in the transmission when a gear in the forwardtravel segment is to be selected. As a result, the vehicle V accordingto the embodiment can more accurately select a gear position having ahigh fuel consumption in the forward travel segment.

When the vehicle V is traveling on an automobile-only road such as ahighway, the vehicle V changes, according to various travelingenvironments where the vehicle V is placed, presence or absence of ashift to the gear position selected by the prefetching. As a result, anuncomfortable feeling, which can be given to a driver due to the shiftof the vehicle V, can be reduced.

<Configuration of Vehicle V According to Embodiment>

An internal configuration of the vehicle V according to the embodimentwill be described with reference to FIG. 2.

FIG. 2 is a diagram schematically showing an internal configuration ofthe vehicle V according to the embodiment. The vehicle V according tothe embodiment includes an engine 1, a transmission 2, a globalpositioning system (GPS) sensor 3, a weight sensor 4, a speed sensor 5,an accelerator opening sensor 6, and a vehicle control device 10 as theECU.

The vehicle V is a large vehicle which uses the engine 1, such as adiesel engine, to provide drive force, and is, in particular, a vehiclehas an automatic cruise mode. The transmission 2 is an AMT fortransmitting rotational drive force of the engine 1 to a drive wheel(not shown) of the vehicle V. The transmission 2 includes a plurality ofpositions of gears for converting the rotational drive force of theengine 1.

Here, the “automatic cruise mode” in the vehicle V refers to a mode inwhich the engine 1, the transmission 2, and the like are automaticallycontrolled by the ECU so as to maintain a speed of the vehicle V set inadvance even if the driver does not operate the accelerator or a shiftlever. It is mainly assumed that the automatic cruise mode is used whenthe vehicle V travels on a highway.

The GPS sensor 3 receives and analyzes radio waves transmitted from aplurality of navigation satellites, so as to acquire a position of theGPS sensor 3, that is, a position of the vehicle V on which the GPSsensor 3 is mounted. The GPS sensor 3 outputs information indicating theposition of the vehicle V to the vehicle control device 10.

The weight sensor 4 acquires total weight of the vehicle V.Specifically, the weight sensor 4 acquires the total weight of thevehicle V by measuring weight of a load of the vehicle V and adding upthe weight of the load and weight of the vehicle V alone excluding theload. The weight sensor 4 outputs information indicating the totalweight of the vehicle V to the vehicle control device 10.

The speed sensor 5 measures the speed of the vehicle V. The speed sensor5 outputs information indicating the measured speed to the vehiclecontrol device 10. The accelerator opening sensor 6 measures anaccelerator opening degree which is a press-down amount of a pedal of anaccelerator by a driver of the vehicle V. The accelerator opening sensor6 outputs information indicating the accelerator opening degree to thevehicle control device 10.

The vehicle control device 10 acquires information from each of thesensors described above, and controls, based on the acquiredinformation, the amount of fuels to be supplied to a cylinder in theengine 1 and the gear positions of the transmission 2. When the vehicleV is in the automatic cruise mode, the vehicle control device 10controls the engine 1 and the transmission 2 so that the vehicle Vtravels at a set speed. In addition, when a speed limit device (SLD) ofthe vehicle V (not shown) is operating, the vehicle control device 10controls the engine 1 and the transmission 2 so that the speed of thevehicle V does not exceed the set maximum speed.

FIG. 3 is a diagram schematically showing a functional configuration ofthe vehicle control device 10 according to the embodiment. The vehiclecontrol device 10 according to the embodiment includes a storage unit 11and a control unit 12.

The storage unit 11 is, for example, a read only memory (ROM), or arandom access memory (RAM). The storage unit 11 stores various programsfor causing the control unit 12 to function. The storage unit 11 maystore map information, and may store information indicating a road slopeof a road.

The control unit 12 is a computational resource such as a centralprocessing unit (CPU; not shown). The control unit 12 achieves functionsof a current gear position selection unit 13, a road slope acquisitionunit 14, a travel segment determination unit 15, a forward gear positionselection unit 16, and a shift control unit 17 by executing a programstored in the storage unit 11.

The current gear position selection unit 13 selects a current gearposition, which is a gear position of the transmission 2 in the segmentwhere the vehicle V is traveling, based on an estimated value of thetravel resistance of the vehicle V on the road on which the vehicle V iscurrently traveling. Details of the current gear position selection bythe current gear position selection unit 13 will be described below.

The road slope acquisition unit 14 acquires, based on the informationindicating the position of the vehicle V acquired from the GPS sensor 3and the map information stored in the storage unit 11, a road slope onthe road on which the vehicle V is currently traveling.

The travel segment determination unit 15 determines, based on the roadslope acquired by the road slope acquisition unit 14, a forward travelsegment ahead of the vehicle V in the travelling direction, which is atravel segment with an average road slope different from that of thecurrent travel segment where the vehicle V is currently travelling, by apredetermined value or more.

The forward gear position selection unit 16 selects a forward gearposition, which is a gear position of the transmission 2 in the forwardtravel segment, based on the road slope of the forward travel segmentand the speed of the vehicle V. Hereinafter, details of the forward gearposition selection by the forward gear position selection unit 16 willbe described together with the current gear position selection by thecurrent gear position selection unit 13.

In order to acquire the slope information of the road on which thevehicle V will travel in the future, the road slope acquisition unit 14must estimate a place where the vehicle V will travel in the future.When the road slope acquisition unit 14 cannot acquire the road slope,the forward travel segment by the travel segment determination unit 15is hardly determined.

When the vehicle V travels on an automobile-only road such as a highway,the road slope acquisition unit 14 is relatively easy to estimate theplace where the vehicle V will travel in the future. In contrast, whenthe vehicle V travels on a road including many branches such as ageneral road and an urban area, the road slope acquisition unit 14hardly estimates the place where the vehicle V will travel in thefuture.

As described above, while the vehicle V is currently traveling on ageneral road, an urban area, or the like, the vehicle V travels inaccordance with the gear selection via the current gear positionselection unit 13. When the vehicle V travels on an automobile-only roadsuch as a highway, the shift control unit 17 acquires a gear selectionresult by the current gear position selection unit 13 and a gearselection result by the forward gear position selection unit 16. Theshift control unit 17 controls a shift of the gear position of thetransmission 2 based on the gear selection result by the current gearposition selection unit 13 and the gear selection result by the forwardgear position selection unit 16.

Hereinafter, the transmission 2 will be described first, and then arelationship between a gear position and fuel consumption will bedescribed. The shift transmission control by the shift control unit 17will be described below.

[Transmission 2 According to the Embodiment]

The transmission 2 provided in the vehicle V according to the embodimentis an AMT, and is a transmission which achieves automatic transmissionof a gear position of the transmission 2 by moving a single rib in amanual transmission according to the related art by an actuator.Therefore, a basic structure of the transmission 2 according to theembodiment is similar to that of a manual transmission according to therelated art. The transmission 2 according to the embodiment includes twosub transmission mechanisms called a splitter and a range, and one maintransmission mechanism provided between the splitter and the range.

The splitter changes a gear ratio between an input shaft, which receivespower of the engine of the vehicle V, and a counter shaft. The maintransmission mechanism mainly changes a gear ratio between a countershaft and an output shaft. The range is provided on a drivingtransmission path for transmitting the rotational driving of an outputshaft to a propeller shaft, and changes a gear ratio between the outputshaft and the propeller shaft. The main transmission mechanism isprovided with a “direct gear” directly coupling the input shaft to theoutput shaft.

In the transmission 2 of the vehicle V according to the embodiment, gearstages of the splitter, the main transmission mechanism, and the rangeare, for example, two stages, three stages, and two stages,respectively. That is, the transmission 2 provided in the vehicle Vaccording to the embodiment is a 12-stage (2 stages×3 stages×2 stages=12stages) transmission. If the 12th-stage gear (overdrive gear) or the11th-stage gear (direct gear) is selected as a gear of the transmission2 when the vehicle V travels around a highway with a small slope, thefuel consumption of the vehicle V may be always increased.

The direct gear is a gear which directly couples the input shaft to theoutput shaft. Since the power of the engine is directly transmitted tothe output shaft not via the counter shaft, the transmission efficiencyis higher than those of other gear positions via the countershaft. Evenwhen the gear position of the transmission 2 is the five stage, the maintransmission mechanism becomes a direct gear. However, a gear ratio ofthe range in this case does not become direct coupling (gear ratio: 1),and the transmission efficiency is decreased. Hereinafter, in thepresent specification, the gear position of the transmission 2 isdefined such that the “overdrive gear” means a gear at the highest stageof the transmission 2, and the “direct gear” means a gear at a stagelower than the highest stage of the transmission 2 by one stage.

[Relationship Between Gear Position and Fuel Consumption]

FIG. 4 is a diagram schematically showing an example of a fuelconsumption contour map of the engine 1 according to the embodiment.Hereinafter, the gear selection in the transmission 2 will be describedwith reference to FIG. 4.

In the fuel consumption contour map shown in FIG. 4, a vertical axisindicates net average effective pressure Pme of a cylinder provided inthe engine 1, and a horizontal axis indicates a rotation speed N of theengine 1. Torque T of the engine 1 is obtained by multiplying the netaverage effective pressure Pme by a predetermined value determined bythe exhaust amount of the engine 1. That is, the net average effectivepressure Pme is proportional to the torque T generated by the engine 1.When a proportional coefficient is α, T=α Pme.

In the fuel consumption contour map shown in FIG. 4, a curve indicatedby a symbol “Pmax” is the maximum combustion pressure curve “Pmax” whichindicates the maximum combustion pressure of the engine 1. The engine 1cannot generate torque exceeding the maximum combustion pressure curve“Pmax” in the fuel consumption contour map shown in FIG. 4.

In the fuel consumption contour map shown in FIG. 4, an area indicatedby hatching shows specific fuel consumption (SFC) of the engine 1. SFCindicates the fuel consumption amount per unit work of the engine 1. Thesmaller the SFC value is, the less fuel with which the engine 1 can dothe same work.

In the fuel consumption contour map shown in FIG. 4, areas havingdifferent specific fuel consumption are identified using hatching. InFIG. 4, an area denoted by hatching H1 indicated by the symbol H1 is anarea with the best specific fuel consumption (that is, the fuelconsumption amount is small), and thereafter, the specific fuelconsumption deteriorates in an order of hatching H2, hatching H3,hatching H4, and hatching H5. In FIG. 4, an illustration of an areawhere the specific fuel consumption is worse than the area denoted bythe hatching H5 is omitted. Hereinafter, the area denoted by thehatching H1 is simply written as an area H1. The same applies to otherareas.

In order for the vehicle V to overcome the travel resistance and travelat a constant speed Vc, force F generated by the torque T generated bythe vehicle V must countervail the travel resistance of the vehicle V.In this case, the engine 1 of the vehicle V is required to output travelresistance horsepower Pv=F Vc. In the fuel consumption contour map shownin FIG. 4, a curve indicated by a symbol Lp is a constant horsepowercurve Lp corresponding to the travel resistance horsepower Pv=F Vc.

When the engine 1 rotating at rotation speed N generates torque T, thehorsepower P output by the engine 1 is P=T N=α Pme N. Therefore, the netaverage effective pressure (Pme) is inversely proportional to therotation speed N of the engine 1. Here, the rotation speed N of theengine 1 is determined by a gear ratio of the gear position selected bythe transmission 2. Therefore, the engine 1 cannot reach any rotationspeed on the constant horsepower curve Lp in an fuel consumption contourmap, and is regulated to a discrete rotation speed determined by thespeed Vc and the gear ratio of the transmission 2.

In FIG. 4, a white circle G12 indicated by a symbol G12 shows a state ofthe engine 1 in a case where the gear position of the transmission 2 isthe 12th stage (that is, an overdrive gear). Similarly, white circlesindicated by the symbols G11, G10, and G9 show states of the engine 1 inthe cases where the gear position is the 11th stage (that is, a directgear), the 10th stage, and the 9th stage, respectively. In a case wherethe gear position of the transmission 2 are the 12th stage and the 11stage, both are contained in the area H2. However, in the case where thegear position is the 12th stage, the state of the engine 1 is closer tothe area H1 and the fuel consumption is good.

As described above, when the speed Vc of the vehicle V and the travelresistance horsepower Pv of the vehicle V are determined, the currentgear position selection unit 13 and the forward gear position selectionunit 16 can define a gear position with good fuel consumption withreference to the fuel consumption contour map.

[Selection of Gear Position by the Current Gear Position Selection Unit13]

The current gear position selection unit 13 estimates an estimated valuePv of the travel resistance of the vehicle V on the road on which thevehicle V is currently traveling. The current gear position selectionunit 13 further refers to the fuel consumption contour map using thespeed of the vehicle V and the estimated value Pv of the travelresistance to select the gear position of the transmission 2.

As described above, the acceleration of the vehicle V during travellingof the vehicle V is proportional to an amount obtained by subtractingthe travel resistance of the vehicle from the drive force of the vehicleV, and is inversely proportional to the weight of the vehicle V. Thecurrent gear position selection unit 13 estimates the net averageeffective pressure Pme, which is generated by the engine 1, from theinjection amount of fuels injected to the engine 1. The current gearposition selection unit 13 acquires the torque T, which is generated bythe engine 1, from the net average effective pressure Pme. The currentgear position selection unit 13 acquires the drive force of the vehicleV from the torque T, the gear ratio of the selected gear position in thetransmission 2, the final reduction ratio, and a diameter of the drivewheel. The current gear position selection unit 13 estimates the travelresistance of the vehicle V from the drive force of the vehicle V, theweight of the vehicle V, and the acceleration of the vehicle V, andselects a gear position with reference to the fuel consumption contourmap.

[Selection of Gear Position by the Forward Gear Position Selection Unit16]

The forward gear position selection unit 16 differs from the currentgear position selection unit 13 in that the travel resistance of thevehicle V is calculated by calculation. Here, the travel resistance ofthe vehicle V is dominated by the sum of rolling resistance of the drivewheel of the vehicle V, the air resistance of the vehicle V, and theslope resistance of the road on which the vehicle V travels. The airresistance of the vehicle V is proportional to the square of the speedof the vehicle V. The slope resistance of the road depends on the slopeof the road on which the vehicle travels and the weight of the vehicleV. The rolling resistance of the drive wheel and the proportionalcoefficient for calculating the air resistance of the vehicle V arestored in the storage unit 11 by a manufacturer of the vehicle V inadvance.

The forward gear position selection unit 16 refers to the mapinformation stored in the storage unit 11, and acquires the slopeinformation of the forward travel segment determined by the travelsegment determination unit 15. The forward gear position selection unit16 acquires the weight of the vehicle V and the speed of the vehicle Vfrom the weight sensor 4 and the speed sensor 5, respectively. As aresult, the forward gear position selection unit 16 calculates the sloperesistance of the vehicle V in the forward travel segment.

The forward gear position selection unit 16 acquires the air resistanceof the vehicle V by multiplying the square of the speed of the vehicle Vby a proportional coefficient. The forward gear position selection unit16 calculates the travel resistance of the vehicle V by adding up theslope resistance of the vehicle V, the air resistance of the vehicle V,and the rolling resistance read from the storage unit 11. Similar to thecurrent gear position selection unit 13, the forward gear positionselection unit 16 selects a gear position in the forward travel segmentfrom the calculated travel resistance and the fuel consumption contourmap.

Here, the forward gear position selection unit 16 refers to differentfuel consumption contour maps in a case where the gear position of thetransmission 2 is a direct gear and in a case where the gear position ofthe transmission 2 is a normal gear to select the forward gear position.

FIGS. 5A and 5B are diagrams showing a difference between a fuelconsumption contour map of a normal gear and a fuel consumption contourmap of a direct gear. Specifically, FIG. 5A is a diagram schematicallyshowing an example of a fuel consumption contour map of a direct gear.FIG. 5B is a diagram schematically showing an example of a fuelconsumption contour map of a normal gear. The fuel consumption contourmap shown in FIG. 5B is the same as the fuel consumption map shown inFIG. 4. In other words, the white circle G12 in the fuel consumptioncontour map of the normal gear shown in FIG. 5B shows a state of theengine 1 in the case of an overdrive gear in which the gear position ofthe transmission 2 is the 12th stage.

As described above, the transmission efficiency of the gear of theentire transmission 2 is increased in the case where the gear positionof the transmission 2 is a direct gear, as compared with the case wherethe gear position of the transmission 2 is a normal gear. Therefore, atransmission loss, which occurs before the output of engine 1 istransmitted to the drive wheels of vehicle V, is reduced in the casewhere the gear position of the transmission 2 is a direct gear, ascompared with the case where the gear position of the transmission 2 isa normal gear. As a result, the specific fuel consumption of the engine1 is improved in the case where the gear position of the transmission 2is a direct gear, as compared with the case where the gear position ofthe transmission 2 is a normal gear.

When the fuel consumption contour map of the direct gear shown in FIG.5A is compared with the fuel consumption contour map of the normal gearshown in FIG. 5B, the area H1 in an area below the maximum combustionpressure curve Pmax in the fuel consumption contour map of the directgear is wider. Therefore, a part which is the area H2 in the fuelconsumption contour map of the normal gear also becomes the area H1 inthe fuel consumption contour map of the direct gear.

A constant horsepower curve Lp shown in FIG. 5A is the same as aconstant horsepower curve Lp shown in FIG. 5B. As shown in FIG. 5A, thestate of the engine 1 in the direct gear (the 11th stage) in theconstant horsepower curve Lp is contained in the area H1. This situationmeans that, in order to make the engine 1 to perform operationcorresponding to the constant horsepower curve Lp, the fuel consumptionof the vehicle V is improved in a case where the transmission 2 adopts adirect gear, as compared with a case where the transmission 2 adopts anormal gear called an overdrive gear.

As described above, the forward gear position selection unit 16 selectsa gear position with reference to the fuel consumption contour mapreflecting the difference in transmission efficiency of the gearposition of transmission 2, so that the gear position which improves thefuel consumption of the vehicle V can be selected more accurately.

[Shift Transmission Control by the Shift Control Unit 17]

When the vehicle V is currently traveling, the current gear positionselection unit 13 always selects an optimal gear position of thetransmission 2 in accordance with a change in the travel resistance ofthe vehicle V. In a case where the vehicle V is traveling on anautomobile-only road such as a highway, the forward gear positionselection unit 16 estimates an optimal gear position in the forwardtravel segment determined by the travel segment determination unit 15while the vehicle V is currently travelling in the current travelsegment.

Therefore, when the vehicle V reaches a boundary between the currenttravel segment and the forward travel segment in a case where thevehicle V is traveling on an automobile-only road such as a highway, aconflict between the current gear position and the forward gear positionmay be occurred. Since the gear ratio of the direct gear is higher thanthe gear ratio of the overdrive gear, the rotation speed of the engine 1in the case of the direct gear is higher even when the speed of thevehicle V is the same. Therefore, for example, when the transmission 2is shifted from the overdrive gear to the direct gear from the viewpointof improving the fuel consumption, the driver of vehicle V may get animpression that engine 1 has suddenly blown up.

Therefore, the shift control unit 17 changes, in accordance with varioustravel environments where the vehicle V is placed, whether or not toshift to the forward gear position when the vehicle V reaches theboundary between the current travel segment and the forward travelsegment. The shift transmission control of the transmission 2 by theshift control unit 17, which is performed in accordance with the varioustraveling environments in which the vehicle V is placed, will bedescribed below.

(First Shift Transmission Control)

It is assumed that the gear position of the transmission 2 in thecurrent travel segment is the overdrive gear and the forward gearposition selected by the forward gear position selection unit 16 is thedirect gear. The shift control unit 17 downshifts the gear position ofthe transmission 2 from the overdrive gear to the direct gear when thevehicle V reaches the forward travel segment, on condition thatestimated travel time of the vehicle V in the forward travel segment islonger than predetermined time.

Here, the “predetermined time” is “downshift determination referencethreshold time”, which is referred to in order to determine whether ornot the shift control unit 17 downshifts the gear position of thetransmission 2 from the overdrive gear to the direct gear at theboundary between the current travel segment and the forward travelsegment. A specific value of the downshift determination threshold timemay be determined by an experiment in consideration of slope informationof a road on which the vehicle V is assumed to travel, performances ofthe engine 1 provided in the vehicle V, and the like, and is, forexample, one minute. This is the time during which the vehicle Vtraveling at 80 km/h travels approximately 1.3 kin.

The shift control unit 17 prevents the downshift in a case where timefor travelling the travel segment where the vehicle V is traveling afterdownshifting from the overdrive gear to the direct gear is shorter thanthe predetermined time, that is, in a case where the estimated traveltime of the vehicle V is short. As a result, the shift control unit 17can prevent the driver of the vehicle V from feeling that the shift isrepeated in a short time.

As described above, the forward gear position selection unit 16calculates the travel resistance of the vehicle V based on the weight ofthe vehicle V, the speed of the vehicle V, the rolling resistance of thevehicle V, and the like, and selects the forward gear position. Here,the forward gear position selection unit 16 may select the direct gearas the best gear, depending on a magnitude of measurement errors of theweight of the vehicle V, the speed of the vehicle V, the rollingresistance of the vehicle V, even in a case where the engine 1 has a lowload (for example, in a case where the vehicle V is currently travelingon a flat road).

When the forward gear position selection unit 16 selects the direct gearas the forward gear position according to miscalculation of the travelresistance in a case the where the vehicle V travels on a road whoseforward travel segment is flat, an unnecessary downshifting is performedat the boundary of the travel segments. The gear ratio of the directgear is larger than the gear ratio of the overdrive gear, so that therotation speed of the engine 1 is increased when the gear position ofthe transmission 2 is downshifted from the overdrive gear to the directgear. Since the increase in the rotation speed of the engine 1 may causea noise, the driving feels of the driver may be impaired.

Therefore, as a condition for downshifting the gear position of thetransmission 2 from the overdrive gear to the direct gear when thevehicle V reaches the forward travel segment, the shift control unit 17may add the fact that road slope in the forward travel segment is anupslope equal to or greater than a predetermined value.

Here, the “upslope equal to or greater than a predetermined value” is a“downshift determination reference threshold slope”, which is referredto in order to determine whether or not the shift control unit 17downshifts the gear position of the transmission 2 from the overdrivegear to the direct gear at the boundary between the current travelsegment and the forward travel segment. A specific value of thedownshift determination reference threshold slope may be determined byan experiment in consideration of slope information of a road on whichthe vehicle V is assumed to travel, performances of the engine 1provided in the vehicle V, and the like, and is, for example, 1%. As aresult, it is possible to prevent the driver of the vehicle V fromfeeling uncomfortable due to unnecessary downshift in the transmission2.

(Second Shift Transmission Control)

It is assumed that the gear position of the transmission 2 in thecurrent travel segment is the direct gear, and the forward gear positionselected by the forward gear position selection unit 16 is also thedirect gear. In this case, it is considered that the current gearposition selection unit 13 newly selects an upshift to the overdrivegear while the vehicle V is currently traveling in the current travelsegment. The shift control unit 17 selects, based on a situation untilthe vehicle V reaches the forward travel segment, whether or not tocause the transmission 2 to upshift before the vehicle V reaches theforward travel segment.

More specifically, when the estimated time until the vehicle V reachesthe forward travel segment is within predetermined time, the shiftcontrol unit 17 maintains the gear position of the transmission 2 as thedirect gear without upshifting even in a case where the current gearposition selection unit 13 newly selects the upshift to the overdrivegear.

Here, the “predetermined time” is “upshift determination referencethreshold time”, which is referred to in order to determine whether ornot the shift control unit 17 upshifts the gear position of thetransmission 2 from the direct gear to the overdrive gear in the currenttravel segment. A specific value of the upshift determination referencethreshold time may be determined by an experiment in consideration ofslope information of a road on which the vehicle V is assumed to travel,performances of the engine 1 provided in the vehicle V, and the like,and is, for example, one minute, which is the same as the downshiftdetermination reference threshold time. The upshift determinationreference threshold time is stored in the storage unit 11.

The shift control unit 17 prevents the upshift in a case where thetravel segment where the vehicle V travels after downshifting from theoverdrive gear to the direct gear is short, that is, in a case where theestimated travel time of the vehicle V is short. As a result, the shiftcontrol unit 17 can prevent the driver of the vehicle V from feeling abusy shift caused by repeated shift in short time.

The shift control unit 17 may determine whether or not to upshift basedon a distance condition instead of or in addition to the time condition.Specifically, when the travel distance until the vehicle V reaches theforward travel segment is within a predetermined distance, the shiftcontrol unit 17 may maintain the gear position of the transmission 2 asthe direct gear even in a case where the current gear position selectionunit 13 newly selects the upshift to the overdrive gear.

Here, the “predetermined distance” is “upshift determination referencethreshold distance”, which is referred to in order to determine whetheror not the shift control unit 17 upshifts the gear position of thetransmission 2 from the direct gear to the overdrive gear in the currenttravel segment. A specific value of the upshift determination referencethreshold distance may be determined by an experiment in considerationof slope information of a road on which the vehicle V is assumed totravel, performances of the engine 1 provided in the vehicle V, and thelike, and is, for example, 1.5 kilometers. This is the distance forwhich the vehicle V traveling at a speed of 90 kilometer/h travels inone minute. As a result, the shift control unit 17 can prevent thedriver of the vehicle V from feeling a busy shift caused by repeatedshift in short time. The upshift determination reference thresholddistance is stored in the storage unit 11.

(Third Shift Transmission Control)

The vehicle V according to the embodiment has an auto cruise mode inwhich the engine 1, the transmission 2, and the like are automaticallycontrolled so as to maintain a preset speed of the vehicle V even if thedriver of the vehicle V does not operate the accelerator or the shiftlever. The speed limit device of the vehicle V controls the engine 1 andthe transmission 2 so that the vehicle V travels at the maximum speedwithout exceeding the set maximum speed. As described above, the vehicleV has a mode in which the vehicle V travels automatically at apredetermined set speed.

The forward gear position selection unit 16 according to the embodimentestimates the travel resistance of the vehicle V on the assumption thatthe vehicle V is traveling at the set speed. In addition, the forwardgear position selection unit 16 refers to a fuel consumption contour mapbased on the rotation speed N of the engine 1 which is calculated on theassumption that the vehicle V is traveling at the set speed. Here, thespeed of the vehicle V is not always equal to the set speed. Forexample, the vehicle V may temporarily accelerate due to overtaking bythe driver of the vehicle V, or the vehicle V may decelerate due to asudden slope. Therefore, in a case where an assumption of the speed ofvehicle V deviates from the actual speed of vehicle V when the forwardgear position selection unit 16 selects the forward gear position, theforward gear position may deviate from an optimum gear position in theforward travel segment.

Therefore, the shift control unit 17 changes the gear position of thetransmission 2 to the gear position selected by the forward gearposition selection unit 16 when the vehicle V reaches the forward travelsegment, on condition that a difference between the predetermined setspeed and the speed of the vehicle V is within a predetermined range.

Here, the “predetermined range” is a “shift determination referencerange”, which is referred to in order to determine whether or not theshift control unit 17 changes the gear position of the transmission 2 tothe gear position selected by the forward gear position selection unit16 at the boundary between the current travel segment and the forwardtravel segment. A specific value of the shift determination referencerange may be determined by an experiment in consideration of slopeinformation of a road on which the vehicle V is assumed to travel,performances of the engine 1 provided in the vehicle V, and the like,and is, for example, 5 kilometer/h. That is, the shift control unit 17changes the gear position to the gear position selected by the forwardgear position selection unit 16 on condition that a value, which isobtained by subtracting a hourly speed of the vehicle V from a sethourly speed, falls within ±5. The shift determination reference rangeis stored in the storage unit 11.

The shift control unit 17 may adopt an auto cruise speed set in thevehicle V as the set speed, or may adopt a speed-limiter speed (speed atwhich the speed limit device operates) preset in the vehicle V as theset speed. In either case, the speed of the vehicle V is expected as aspeed to be adopted when the vehicle V is in the automatic travellingmode. The shift control unit 17 can increase the effectiveness of theforward gear position by performing the shift to the forward gearposition on condition that the difference between the set speed and thespeed of the vehicle V is within a predetermined range.

(Fourth Shift Transmission Control)

As described above, the current gear position selection unit 13estimates the travel resistance of the vehicle V from the drive force ofthe vehicle V, the weight of the vehicle V, and the acceleration of thevehicle V, and selects the gear position with reference to the fuelconsumption contour map. The current gear position selection unit 13 mayestimate the travel resistance in real time while the vehicle V iscurrently traveling, and may select the current gear position by readingand referring to a shift pattern, in which a relationship between thespeed of the vehicle V and the gear position of the transmission 2 ispatterned, from the storage unit 11. In the following description, theaspect that the current gear position selection unit 13 selects thecurrent gear position, which is the gear position of the transmission 2in the current travel segment, in accordance with the shift patterndetermined in advance and stored in the storage unit 11 will bedescribed as a premise.

The shift pattern stored in the storage unit 11 is not based on ageneral-purpose fuel consumption contour map, and the fuel consumptioncontour map is not referred to.

Here, it is assumed that the gear position of the transmission 2 in thecurrent travel segment is an overdrive gear and the forward gearposition is a direct gear. In a case where the vehicle V ends thetraveling in the current travel segment and starts the travelling in theforward travel segment, that is, in a case where the travel segment as aforward travel segment where the shift control unit 17 selects theforward gear becomes the “current travel segment”, discords are likelyto occur between a current gear selected by the current gear positionselection unit 13 and a forward gear selected by the shift control unit17 in advance. This is because the fuel consumption contour map is notconsidered in a general-purpose shift map.

Therefore, when the gear position of the transmission 2 in the currenttravel segment is the overdrive gear and the forward gear position isthe direct gear, the shift control unit 17 maintains the gear positionof the transmission 2 as the direct gear while the vehicle V iscurrently travelling in a forward travel segment. The shift control unit17 downshifts the gear position of the transmission 2 to the direct gearwhen the vehicle V reaches the forward travel segment, and maintains thegear position of the transmission 2 as the direct gear even if thecurrent gear position selection unit 13 selects the overdrive gear whilethe vehicle V is currently travelling in the forward travel segment(that is, a current travel segment) during forward gear selection by theforward gear position selection unit 16. As a result, it is possible toprevent the gear position of the transmission 2 from being selectedalternately between the current gear position and the pre-selectedforward gear position.

The shift control unit 17 can perform the above-described four shifttransmission controls from the first shift transmission control to thefourth shift transmission control in any combination. The new shifttransmission control generated by the combination has an effect oforiginal shift control.

<Effect of Vehicle Control Device 10>

As described above, according to the vehicle control device 10 of theembodiment, it is possible to improve estimation accuracy of the fuelconsumption amount and the technique of selecting the gear position inthe vehicle V provided with the AMT. In particular, the forward gearposition selection unit 16 according to the embodiment selects theforward gear position with reference to different fuel consumptioncontour maps in consideration of the difference in gear transmissionefficiency, in both a case where the gear position of the transmission 2is the direct gear and a case where the gear position of thetransmission 2 is the normal gear. As a result, the forward gearposition selection unit 16 can improve the estimation accuracy of thefuel consumption amount in the vehicle V.

Further, when the vehicle V is traveling on an automobile-only road suchas a highway, the shift control unit 17 changes whether or not to shiftto the forward gear position selected by the forward gear positionselection unit 16 in accordance with various traveling environmentswhere the vehicle V is placed. As a result, an uncomfortable feeling,which can be given to a driver due to the shift of the vehicle V, can bereduced.

The present disclosure have been described using the embodiment, but thetechnical scope of the present disclosure is not limited to theabove-described embodiment and various modifications and changes can bemade within the scope of the present disclosure. For example, thespecific embodiment of the dispersion and integration of the device isnot limited to the above embodiment, and all or a part of the embodimentmay be functionally or physically distributed and integrated in optionalunits. In addition, new embodiments generated by any combination of aplurality of embodiments are also contained in the embodiment of thepresent disclosure. The effect of the new embodiment caused by thecombination has the effect of the original embodiment.

This application is based on Japanese Patent Application (No.2017-095974) filed on May 12, 2017, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The vehicle control device according to the present disclosure is usefulin improving a technique of selecting the gear position in a vehicleprovided with an automated manual transmission.

LIST OF REFERENCE NUMERALS

-   -   1 engine    -   2 transmission    -   3 GPS sensor    -   4 weight sensor    -   5 speed sensor    -   6 accelerator opening sensor    -   10 vehicle control device    -   11 storage unit    -   12 control unit    -   13 current gear position selection unit    -   14 road slope acquisition unit    -   15 travel segment determination unit    -   16 forward gear position selection unit    -   17 shift control unit    -   V vehicle

1. A vehicle control device that controls operation of a vehicleprovided with a transmission, the transmission includes: a direct gearthat transmits engine power, which is input via an input shaft, to anoutput shaft not via a counter shaft, and that directly couples theinput shaft to the output shaft; and a normal gear that transmits theengine power to the output shaft via the counter shaft, and thatincludes an overdrive gear having a gear ratio lower than a gear ratioof the direct gear, and the vehicle control device comprises: a travelsegment determination unit that determines a forward travel segmentahead of the vehicle in a travelling direction, the forward travelsegment having a road slope different from a road slope of a currenttravel segment where the vehicle currently travels; a current gear stageselection unit that selects a current gear position, which is a gearposition of the transmission in the current travel segment, inaccordance with a pre-defined shift pattern; a forward gear positionselection unit that selects a forward gear position, which is a gearposition of the transmission in the forward travel segment, based on atravel resistance of the vehicle in the forward travel segment estimatedbased on a road slope of the forward travel segment and a speed of thevehicle; and a shift control unit that maintains a gear position of thetransmission as the direct gear while the vehicle travels in the forwardtravel segment, when a gear position of the transmission in the currenttravel segment is the overdrive gear and the forward gear position isthe direct gear.
 2. The vehicle control device according to claim 1,wherein the shift control unit downshifts a gear position of thetransmission to the direct gear when the vehicle reaches the forwardtravel segment, and maintains the gear position of the transmission asthe direct gear even in a case where the current gear position selectionunit selects the overdrive gear while the vehicle travels in the forwardtravel segment.
 3. The vehicle control device according to claim 1,wherein the shift control unit downshifts a gear position of thetransmission to the direct gear when the vehicle reaches the forwardtravel segment, on condition that a road slope in the forward travelsegment is an upslope equal to or greater than a predetermined value.